Triblock copolymers with acidic groups

ABSTRACT

Triblock copolymers useful for forming ion conductive membranes are provided. The triblock copolymers are characterized by having either a hydrophobic-hydrophilic -hydrophobic or a hydrophilic-hydrophobic-hydrophilic polymer sequence that induces a microphase separated morphology. Variations in which the hydrophilic polymer sequence component includes either acid groups or salts of acid groups are also disclosed. Methods for forming an ion conductive membrane from the triblock copolymers are provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. application Ser. No. 11/120,710filed May 3, 2005, now U.S. Pat. No. 7,977,394, issued Jul. 12, 2011,the disclosure of which is incorporated in its entirety by referenceherein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to triblock copolymers that are formableinto ion conductive membranes useful in PEM fuel cells.

2. Background Art

Fuel cells are used as an electrical power source in many applications.In particular, fuel cells are proposed for use in automobiles to replaceinternal combustion engines. In proton exchange membrane (“PEM”) typefuel cells, hydrogen is supplied to the anode of the fuel cell andoxygen is supplied as the oxidant to the cathode. The oxygen can beeither in a pure form (O₂) or air (a mixture of O₂ and N₂). PEM fuelcells typically have a membrane electrode assembly (“MEA”) in which asolid polymer membrane has an anode catalyst on one face and a cathodecatalyst on the opposite face. The MEA, in turn, is sandwiched between apair of non-porous, electrically conductive elements or plates which (1)serve as current collectors for the anode and cathode, and (2) containappropriate channels and/or openings formed therein for distributing thefuel cell's gaseous reactants over the surfaces of the respective anodeand cathode catalysts.

In order to efficiently produce electricity, the polymer electrolytemembrane of a PEM fuel cell typically, must be thin, chemically stable,proton transmissive, non-electrically conductive, and gas impermeable.Moreover, during operation of the fuel cell, the PEM is exposed torather severe conditions, which include, hydrolysis, oxidation andreduction (hydrogenation) that can lead to degradation of the polymerthereby reducing the lifetime of a polymer electrolyte membrane. Thecombination of these requirements imposes rather strict limitations onmaterial choices for these membranes. Presently, there are relativelyfew polymer systems that provide even marginally acceptable results forthe combination of these requirements. An example of a PEM is the Nafionmembrane developed by DuPont in 1966 as a proton conductive membrane.This membrane is possibly the only advanced polymer electrolytecurrently available for use in a membrane electrode assembly in a fuelcell.

Other polymer systems that may be used in PEM applications are found inU.S. Pat. No. 4,625,000 (the '000 patent), U.S. Pat. No. 6,090,895 (the'895 patent), and EP Patent No. 1,113,517 A2 (the '517 patent). The '000discloses a sulfonation procedure forming poly(ether sulfone)s that maybe used in solid polymer electrolyte application. However, the '000patent's post-sulfonation of preformed polymers offers little control ofthe position, number, and distribution of the sulfonic acid groups alongthe polymer backbone. Moreover, the water uptake of membranes preparedfrom post sulfonated polymers increases, leading to large dimensionalchanges as well as a reduction in strength as the degree of sulfonationincreases.

The '895 patent discloses a process for making cross linked acidicpolymers of sulfonated poly(ether ketone)s, sulfonated poly(ethersulfone)s, sulfonated polystyrenes, and other acidic polymers by crosslinking with a species which generates an acidic functionality. However,this reference does not suggest an effective way to cast membranes fromthose cross linked sulfo-pendent aromatic polyethers.

The '517 patent discloses a polymer electrolyte containing a blockcopolymer comprising blocks having sulfonic acid groups and blockshaving no sulfonic acid groups formed by post sulfonation of precursorblock copolymers consisting of aliphatic and aromatic blocks. In thispatent, the precursor block copolymers are sulfonated using concentratedsulfuric acid, which leads to the sulfonation of aromatic blocks.However, once again, this post sulfonation of aromatic blocks offers thelittle control of the position, number, and distribution of the sulfonicacid groups along the polymer backbone. Furthermore, this postsulfonation of precursor block copolymers also leads to the cleavage ofchemical bonds of the aliphatic block.

Although some of the proton conducting membranes of the prior artfunction adequately in hydrogen fuel cells, these membranes tend torequire high humidity (up to 100% relative humidity) for efficientlong-term operation. Moreover, prior art membranes are not able toefficiently operate at temperatures above 80° C. for extended periods oftime. This temperature limitation necessitates that these membranes beconstantly cooled and that the fuel (i.e., hydrogen) and oxidant behumidified.

Accordingly, there exists a need for improved materials for formingpolymer electrolyte membranes and for methods of forming such materials.

SUMMARY OF THE INVENTION

The present invention overcomes the problems encountered in the priorart by providing in one embodiment a triblock copolymer that can beformed into an ion-conductive membrane. Triblock copolymers useful forforming ion conductive membranes are provided. The triblock copolymersare characterized by having either a hydrophobic-hydrophilic-hydrophobicor a hydrophilic-hydrophobic-hydrophilic polymer sequence that induces amicro-phase separated morphology. The triblock copolymer of thisembodiment comprises a polymer having formula 1:A_(m)-B_(n)-C_(p)  1wherein:

-   -   A is a first polymer segment that is repeated m times to form        first polymer block A_(m) that is either hydrophobic or        hydrophilic;    -   B is a second polymer segment that is repeated n times to form        second polymer block B_(n) that is either hydrophobic or        hydrophilic;    -   C is a third polymer segment that is repeated p times to form        third polymer block C_(p) that is either hydrophobic or        hydrophilic; and    -   m, n, and p are each independently integers from 1 to 200; with        the proviso that when A is hydrophobic, B is hydrophilic and C        is hydrophobic; or when A is hydrophilic, B is hydrophobic and C        is hydrophilic. Moreover, when A is hydrophilic, A comprises a        first substituent for proton transfer, when B is hydrophilic, B        includes a second substituent for proton transfer, and when C is        hydrophilic, C includes a third substituent for proton transfer.

In another embodiment of the invention, an ion conducting membraneincorporating the block copolymers of the invention is provided. The ionconducting membrane is advantageously useable in a fuel cell, and inparticular, a hydrogen fuel cell, operating continuously at temperaturesup to about 120° C. Membranes formed from the block copolymers of theinvention are characterized by having a microphase separated morphologydue to the alternating hydrophobic and hydrophilic polymer sequences.Moreover, the ion conducting membranes of this embodiment have higherproton conductivities at low relative humidities than random copolymersof similar composition.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 provides plots that compare specific conductivities vs.determined IEC at 80° C. and 26% r.h: squares correspond to a multiblockcopolymer with hydrophilic block having formula 8 and hydrophobic blockhaving formula 17; circles correspond to a triblock copolymer with ahydrophilic block (B_(m)) having formula 8 and hydrophobic blocks (A_(n)and C_(m)) having formula 17; triangles correspond to a triblockcopolymer with a hydrophilic block (B_(m)) having formula 9 andhydrophobic block having formula 17, and diamonds correspond to nafion;and

FIG. 2 provides plots that compare water uptake at room temperature vs.determined IEC: squares correspond to a multiblock copolymer withhydrophilic block having formula 8 and hydrophobic block having formula17; circles correspond to a triblock copolymer with hydrophilic block(B_(m)) having formula 8 and hydrophobic block (A_(n) and C_(m)) havingformula 17; triangles correspond to a triblock copolymer withhydrophilic block (B_(m)) having formula 9 and hydrophobic block (A_(n)and C_(m)) having formula 17.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Reference will now be made in detail to presently preferred compositionsor embodiments and methods of the invention, which constitute the bestmodes of practicing the invention presently known to the inventors.

The term “block” as used herein means a portion of a macromolecule,comprising many constitutional units, that has at least one featurewhich is not present in adjacent portions.

The term “block macromolecule” as used herein means a macromolecule thatis composed of blocks in linear sequence.

The term “block polymer” as used herein means a substance composed ofblock macromolecules.

The term “block copolymer” as used herein means a polymer in whichadjacent blocks are constitutionally different, i.e., each of theseblocks comprises constitutional units derived from differentcharacteristic species of monomer or with different composition orsequence distribution of constitutional units.

The term “random copolymer” as used herein means a copolymer consistingof macromolecules in which the probability of finding a given monomericunit at any given site in the chain is independent of the nature of theadjacent units.

In an embodiment of the invention, a triblock copolymer for use as asolid polymer electrolyte is provided. In particular, the triblockcopolymers of the invention are particularly useful for forming ionconductive membranes to be used in PEM fuel cells. The block copolymersof this embodiment are characterized by having a sequence comprising ahydrophobic block, a hydrophilic block, and a hydrophobic block joinedtogether in that order or a sequence comprising a hydrophilic block, ahydrophobic block, and a hydrophilic block joined together in thatorder. The hydrophobic and hydrophilic sequences are immiscible therebyinducing a microphase separated morphology in films cast from thesematerials. This morphology includes, for example, morphologies such asspheres, cylinders, lamellae, ordered bi-continuous double diamondstructures, disordered bicontinuous structures, and combinationsthereof. The block copolymer of the invention comprises a polymer havingformula 1:A_(m)-B_(n)-C_(p)  1wherein:

-   -   A is a first polymer segment that is repeated m times to form        first polymer block A_(m) that is either hydrophobic or        hydrophilic;    -   B is a second polymer segment that is repeated n times to form        second polymer block B_(n) that is either hydrophobic or        hydrophilic;    -   C is a third polymer segment that is repeated p times to form        third polymer block C_(p) that is either hydrophobic or        hydrophilic; and    -   m, n, and p are each independently integers from 1 to 200.        The block copolymer described by formula 1 is further limited by        the proviso that when A is hydrophobic, B is hydrophilic and C        is hydrophobic. Similarly, when A is hydrophilic, B is        hydrophobic and C is hydrophilic. Consistent with these two        provisos, when A is hydrophilic, A includes a first substituent        for proton transfer, when B is hydrophilic, B includes a second        substituent for proton transfer, and when C is hydrophilic, C        includes a third substituent for proton transfer.

The first, second, and third substituents for proton transfer eachindependently include when present an acidic substituent or saltthereof. Examples of suitable substituents for proton transfer include—SO₃H, —SO₃ ⁻M⁺, —COOH, —COO⁻M⁺, —PO₃H₂, —PO₃H⁻M⁺, —PO₃ ²⁻M₂ ⁺, —PO₃²⁻M²⁺, and combinations thereof. Sulfonic and phosphonic acid groups andsalts thereof have been found to be particularly useful in thisembodiment. In these examples, M is a metal such as an alkali oralkaline-earth metal. Particularly useful metals are sodium, potassium,lithium, and the like.

In a variation of the invention, the first block A_(m) has a molecularweight from about 5×10² to about 5×10⁵ (g/mol), the second polymer blockB_(n) has a molecular weight from about 5×10² to about 5×10⁵ (g/mol),and the third polymer block C_(n) has a molecular weight from about5×10² to about 5×10⁵ (g/mol). Moreover, the triblock copolymer of theinvention is characterized by having alternating hydrophobic andhydrophilic blocks. For example, when A_(m) and C_(k) are bothhydrophilic, A and C are each independently described by formula 2 orwhen B_(n) is hydrophilic, B is described by formula 2:

wherein:

-   -   Y¹ is —O—, —S—, —CO—, —SO₂—, —C(CH₃)₂—, —C(CF₃)₂—, —PO(T¹)-,        —C(CH₃)(T¹)-, —PO(R⁴)—, diphenyl methylene, diphenyl silicon,        fluorenyl, an alkylene, a bond directly to the next aromatic        ring, or

-   -   R¹, R², and R³ are each independently H, C₁₋₁₀ alkyl, C₆₋₁₈        aryl, C₆₋₁₈ aralkyl, —SO₃H, —SO₃ ⁻M⁺, —COOH, —COO⁻M⁺, —PO₃H₂,        —PO₃H⁻M⁺, —PO₃ ²⁻M₂ ⁺, or —PO₃ ²⁻M²⁺;    -   R⁴ is H, C₁₋₁₀ alkyl, C₆₋₁₈ aryl, or C₆₋₁₈ aralkyl;    -   T¹ is H or a moiety having at least one substituent for proton        transfer; and    -   i is an integer from 1 to 6.        Polymer segment B having formula 2 is further limited by the        proviso that when i>1, the Y¹ between sequential aromatic rings        are the same or different; the T¹ on sequential aromatic rings        are the same or different; and the R¹, R², and R³ on sequential        aromatic rings are the same or different. Moreover, for at least        one aromatic ring in formula 2, either T₁ is not H or one of R¹,        R², and R³ is —SO₃H, —SO₃ ⁻M⁺, —COOH, —COO⁻M⁺, —PO₃H₂, —PO₃H⁻M⁺,        —PO₃ ²⁻M₂ ⁺, or —PO₃ ²⁻M²⁺. The presence of a phosphonic acid        group or related salt (i.e., —PO₃H₂, —PO₃H⁻M⁺, —PO₃ ²⁻M₂ ⁺, or        —PO₃ ²⁻M²⁺) in T¹ or in R¹, R², and R³ is particularly useful.        In a variation of this embodiment, at least one of R¹, R², and        R³ is —PO₃H₂, —PO₃H⁻M⁺, —PO₃ ²⁻M₂ ⁺, or —PO₃ ²⁻M²⁺. Since        phosphonic acid is a dibasic acid with a weakly dissociating        second acid group, an alternative mechanism for proton transport        that is not possible in monobasic acids such as sulfonic acid,        is available. Moreover, this mechanism is expected to operate        even at low water contents. Accordingly, such polymers exhibit        higher proton conductivity at a lower humidity and water content        than polymers of similar structure with sulfonic acid groups.        Although the beneficial effects of using phosphonic acid groups        are not limited to any particular mechanism, the proton        transport mechanism in the presence of phosphonic acid groups is        believed to be a Grotthus mechanism that operates through chains        of hydrogen bonds thereby requiring a non-dissociated group.

In a particularly useful variation of this embodiment, T₁ is describedby formula 3:

wherein:

-   -   Y² is —O—, —S—, —CO—, —SO₂—, —C(CH₃)₂—, —C(CF₃)₂—, —PO(R⁴)—,        diphenyl methylene, diphenyl silicon, fluorenyl, an alkylene, or        a bond directly to the next aromatic ring;    -   R⁵, R⁶, R⁷, R⁸, R⁹, R¹⁰, R¹¹, R¹², and R¹³ are each        independently H, C₁₋₁₀ alkyl, C₆₋₁₈ aryl, C₆₋₁₈ aralkyl, SO₃H,        —SO₃ ⁻M⁺, —COOH, —COO⁻M⁺, —PO₃H₂, —PO₃H⁻M⁺, —PO₃ ²⁻M₂ ⁺, and        —PO₃ ²⁻M²⁺;    -   R⁴ is H, C₁₋₁₀ alkyl, C₆₋₁₈ aryl, or C₆₋₁₈ aralkyl;    -   M is a metal, ammonium, or alkylammonium; and    -   j is an integer from 1 to 30.        Formula 3 which describes side chain T¹ is further limited by        the proviso that when j>1, the Y² between sequential aromatic        rings are the same or different and the R⁵, R⁶, R⁷, R⁸, and R⁹        on sequential aromatic rings are the same or different.        Moreover, at least one of R⁵, R⁶, R⁷, R⁸, R⁹, R¹⁰, R¹¹, R¹², and        R¹³ is —SO₃H, —SO₃ ⁻M⁺, —COOH, —COO⁻M⁺, —PO₃H₂, —PO₃H⁻M⁺, —PO₃        ²⁻M₂ ⁺, or —PO₃ ²⁻M²⁺. In this variation, T¹ includes acidic        groups on spacers. Spacers are side chains that position the        acidic groups at a distance from a main chain. This positioning        on spacers allows for the acidic groups to arrange themselves in        orientations suitable for proton dissociation at low water        levels through neighboring-group interactions. In a variation of        this embodiment, Y¹ in formula 2 and Y² in formula 3 (for T¹)        are —S— and —SO₂—. In another variation of this embodiment,        acidic groups are not present in formula A, B, or C. In this        variation, —O— and —CO— are present in the hydrophilic blocks.

Similarly, when A and C are both hydrophobic, A and C are eachindependently described by formula 4 or when B is hydrophobic, B isdescribed by formula 4:

wherein:

Y³ is —O—, —S—, —CO—, —SO₂—, —C(CH₃)₂—, —C(CF₃)₂—, —PO(T¹)-,—C(CH₃)(T¹)-, —PO(R⁴)—, diphenyl methylene, diphenyl silicon, fluorenyl,an alkylene, a bond directly to the next aromatic ring, or

R¹⁴, R¹⁵, R¹⁶, and R¹⁷ are each independently H, C₁₋₁₈ alkyl, C₆₋₁₈aryl, and C₆₋₁₈ aralkyl;

R⁴ is H, C₁₋₁₀ alkyl, C₆₋₁₈ aryl, or C₆₋₁₈ aralkyl; and

k is an integer from 1 to 30.

The hydrophobic polymer segment that is described by formula 4 isfurther limited by the proviso that when k>1, the Y₃ between sequentialaromatic rings are the same or different, and the R¹⁴, R¹⁵, R¹⁶, and R¹⁷on sequential aromatic rings are the same or different. In at least onerelatively preferred variation of this embodiment, R¹⁴, R¹⁵, R¹⁶, andR¹⁷ are each H.

As set forth above, formula 2 provides examples of hydrophilic blocks.Specific examples when A, B, or C are hydrophilic are given by formulae5 through 16 and salts thereof:

As set forth above, formula 4 provides examples of hydrophobic blocks.Specific examples when A, B, or C are hydrophobic are provided byformulae 17 through 20 and salts thereof:

In another embodiment of the invention, a triblock copolymer isprovided. The triblock copolymer of this embodiment is described byformula 1:A_(m)B_(n)C_(p)1  1wherein:

-   -   when A_(m) and C_(p) are both hydrophilic, A and C are each        independently described by formula 21 and B is a hydrophobic        polymer segment; or when B_(n) is hydrophilic, B is described by        formula 21 and A and C are each independently hydrophobic        polymer segments:

-   -   m, n, and p are integers;    -   R¹⁹, R²⁰, R²¹, R²², R²³, R²⁴, R²⁵, R²⁶, R²⁷, R²⁸, R²⁹, R³⁰, R³¹,        R³², R³³, and R³⁴ are each independently H, —SO₃H, —SO₃ ⁻M⁺,        —COOH, —COO⁻M⁺, —PO₃H₂, —PO₃H⁻M⁺, —PO₃ ²⁻M₂ ⁺, or —PO₃ ²⁻M²⁺;        and    -   M is a metal, ammonium or alkylammonium as set forth above. In a        variation of this embodiment, m, n, and p are each independently        an integer from about 1 to about 200.

In an analogous manner as set forth above, when A_(m) and C_(p) are bothhydrophobic, A and C are each independently described by formula 4 orwhen B_(n) is hydrophobic, B is described by formula 4:

wherein:

-   -   Y³ is —O—, —S—, —CO—, —SO₂—, —C(CH₃)₂—, —C(CF₃)₂—, —PO(T¹)-,        —C(CH₃)(T¹)-, —PO(R⁴)—, diphenyl methylene, diphenyl silicon,        fluorenyl, an alkylene, a bond directly to the next aromatic        ring, or

-   -   T¹ and R⁴ are defined above;    -   R¹⁴, R¹⁵, R¹⁶, and R¹⁷ are each independently H, C₁₋₁₈ alkyl,        C₆₋₁₈ aryl, or C₆₋₁₈ aralkyl; and    -   k is an integer from about 1 to about 30 less than m.        The polymer segment described by formula 4 is further limited by        the proviso that when k>1, the Y³ between sequential aromatic        rings are the same or different and the R¹⁴, R¹⁵, R¹⁶, and R¹⁷        on sequential aromatic rings are the same or different.

In another embodiment of the invention, the triblock copolymers setforth above are used to form an ion conductive membrane. As set forthabove, the block copolymers of the invention are characterized by havingeither a hydrophobic-hydrophilic-hydrophobic sequence or ahydrophilic-hydrophobic-hydrophilic sequence that induces a microphaseseparated morphology when the polymers are formed into films. Due tothis microphase separated morphology, the polymer segments with acidicgroups are associated in hydrophilic domains that contain essentially nohydrophobic segments. Moreover, the local concentration of acidic groupsin the hydrophobic domains is higher than in a randomly sulfonatedpolymer such as sulfonated poly(ether ether ketone) (“SPEEK”). Moreover,water taken up by membranes will be present only in the hydrophilicdomains and not in hydrophobic domains. Therefore, at a given overallion exchange capacity (“IEC”) value and water content, the blockcopolymers will contain a higher local IEC and water level within thehydrophilic domains than compared to random copolymers. The microphaseseparated morphology includes, for example, morphologies such asspheres, cylinders, lamellae, ordered bi-continuous double diamondstructures, disordered bicontinuous structures, and combinationsthereof. The method of making such membranes begins first withpreparation of the triblock copolymer. In a first variation of thisembodiment, a first polymer having formula 22 is prepared:

wherein Z¹ and Z² are each independently —H, —SH, —S(O)N(R¹⁸)₂, F, Cl,Br, I, —NO₂, or —OH; R¹⁸ is H, C₁₋₁₀ alkyl, cycloalkyl, C₆₋₁₈ aryl, orC₆₋₁₈ aralkyl; and T¹, R¹, R², R³, Y¹, and i are the same as that setforth above. Similarly, an end functionalized second polymer blockhaving formula 23 is also synthesized:

wherein Z³ and Z⁴ are each independently —H, —SH, —S(O)N(R¹⁸)₂, F, Cl,Br, I, —NO₂, or —OH; R¹⁸ is H, C₁₋₁₀ alkyl, cycloalkyl, C₆₋₁₈ aryl, orC₆₋₁₈ aralkyl; and R¹⁴, R¹⁵, R¹⁶, R¹⁷, Y³, and k are the same as thatset forth above. In this variation, one of the block polymer havingformula 22 or the block polymer having formula 23 must bemonofunctional. Accordingly, one of Z¹, Z², Z³ or Z⁴ must be H. Thetriblock copolymers of the invention are then prepared by reactingpolymer block 22 with polymer block 23.

In another variation of the invention, the polymer block having formula23 is reacted with one or more monomers suitable for forming the polymerblock having formula 22. Specifically, the triblock copolymers of theinvention having formula 1 are prepared by synthesizing anend-functionalized polymer block having formula 23:

wherein Z³ and Z⁴ are each independently —H, —SH, —S(O)N(R¹⁸)₂, F, Cl,Br, I, —NO₂, or —OH; R¹⁸ is H, C₁₋₁₀ alkyl, cycloalkyl, C₆₋₁₈ aryl, orC₆₋₁₈ aralkyl; and R¹⁴, R¹⁵, R¹⁶, R¹⁷, Y³, and k are the same as setforth above. Next, the polymer block having formula 23 is reacted withone or more monomers that polymerize into a block having formula 2:

to form the block copolymer having formula 1, wherein T¹, R¹, R², R³,Y¹, and i are the same as set forth above.

In yet another variation of this embodiment, the polymer block havingformula 22 is reacted with one or more monomers suitable for forming thepolymer block having formula 23. Specifically, the block copolymers ofthis embodiment are formed by synthesizing an end-functionalized polymerblock having formula 22:

wherein Z¹ and Z² are each independently —H, —SH, —S(O)N(R¹⁸)₂, F, Cl,Br, I, —NO₂, or —OH; R¹⁸ is H, C₁₋₁₀ alkyl, cycloalkyl, C₆₋₁₈ aryl, orC₆₋₁₈ aralkyl; and R¹, R², R³, Y¹, and i are the same as set forthabove. Next, the polymer block having formula 22 is reacted with one ormore monomers that polymerize into a block having formula 4:

to form the triblock copolymer having formula 1. R¹⁴, R¹⁵, R¹⁶, R¹⁷, Y³,and k are the same as set forth above.

In an example of the preparation of the block copolymer of theinvention, the hydrophobic first polymer block having formula 23 issynthesized using one or more non-sulfonated bis-functional monomers anda monofunctional endcapper. A monofuntional endcapper is used to makesure that one of the end groups Z¹ through Z⁴ is —H. Whilebis-functional monomers typically include two groups that are halogens(F, Cl, Br, I), or SH or OH, the monofunctional endcapper includes onlyone such group. Examples of useful bifunctional monomers include4,4′-difluorobenzophenone, 2,2-bis-(4-hydroxy-phenyl)-propane,1,3-bis-(4-fluorbenzoyl)benzene,4,4′-(hexafluoroisopropylidene)-diphenol, 4,4′-difluorobenzophenone,bis-(4-fluorophenyl)-sulfone, 4,4′-thiobisbenzenethiol, and the like.Examples of useful monofunctional endcapper molecules include cresolssuch as p-cresol, phenol, alcohols such as methanol, arylhalides such as4-fluorobenzophenone, 4-chlorodiphenylsulfone, and the like. Themolecular mass (i.e. number of repeating units) of the block is adjustedby using a defined stoichiometric ratio between the difunctionalmonomers and the endcapper in a molar ratio from 1:1 to 200:1(monomers:endcapper). After the reaction is completed, the hydrophobicfirst triblock copolymer is isolated by precipitation in a solvent suchas methanol and washed with excess amounts of the solvent and then withwater. Next, the dried hydrophobic first block is reacted with a monomerthat includes at least one substituent for proton transfer. Optionally,one or more additional bis-functional monomers that may or may notinclude substituents for proton transfer are also reacted with the firstblock. In order to adjust the composition of the triblock the necessaryratio between the monomers building the hydrophilic block and thehydrophobic endblock is used. The polymer is isolated by precipitationand purified in the same manner by precipitation into alcohol as for theendblocks but without washing with water since the triblocks especiallywhen having a large hydrophilic middleblock swell when in contact withwater which results in difficulties in filtering the polymer. Theyielded polymer flakes are thoroughly dried.

Regardless of the method by which the block copolymers of the inventionare formed, the block copolymers are eventually formed or cast into anion conductive membrane suitable for fuel cell applications. The polymercan be cast from solution in its acid, acid halide or salt form. Inaddition, a membrane can also be formed by hot pressing or by meltextrusion of the polymer. The behavior of the polymer during hotpressing or during melt extrusion can be improved by transferring theacidic groups in the polymer into ester groups or other protectivegroups, which can be returned into acid groups after melt processing. Inone variation, the acid groups of the block copolymer are transformed toacid halide groups to form a modified block copolymer. Then a film iscast from a solution of the modified block copolymer onto a substrate.Finally, the acid halide groups are transformed back into the acidgroups to form the ion conductive membrane. After formation of themultiblock copolymers of the present invention ion conductive membranescan be formed. In a first refinement of this embodiment, the driedpolymer is dissolved in a suitable solvent (i.e., DMSO). The polymersolution is then poured into a Petri dish and is covered with a lid insuch a way that there is a small gap between the dish and the lid toallow for slow evaporation of the solvent. In another refinement, thedried polymer is also dissolved in a suitable solvent to form a viscoussolution. The viscous solution is spread onto a glass plate and broughtto a uniform thickness by means of a doctor blade. For both theserefinements, the solvent is then removed by drying at elevatedtemperature in an oven. Finally, the morphology is adjusted by annealingthe membrane at an elevated temperature. Typically, this annealing isperformed at reduced pressures or in a vacuum. Useful annealingtemperatures are either between the glass transition or meltingtemperatures of the two block types, or between the highest of the glasstransition or melt temperatures of the two block types and theorder-disorder transition temperature (if present). Temperatures betweenabout 100° C. and 300° C. are useful with an optimal annealingtemperature being about 200° C. In some variations of the invention,after polycondensation steps, the multiblock copolymer of the inventionis obtained as a sulfonic acid salt or phosphorus acid salt. Thereforethe membrane has to be converted into its free sulfonic acid form priorto use. This conversion is accomplished by treating the membranes with adiluted acid (e.g. 1 molar sulfuric acid) for 24 hours. Afterwards themembranes are rinsed thoroughly with DI water to remove excess acid.

The following examples illustrate the various embodiments of the presentinvention. Those skilled in the art will recognize many variations thatare within the spirit of the present invention and scope of the claims.

Ion conducting membranes formed by the polymers set forth in theexamples can be characterized by the ion exchange capacity (“IEC”),water uptake, and specific conductivity.

1. Determination of the TEC by Titration:

Membrane pieces in the sulfonic acid form are dried at 120° C. andvacuum for at least 2 hours. About 100 mg of the polymer and 50 ml ofaqueous LiCl solution with a concentration of 2 mol/l are put into anErlenmeyer flask with a cover. The closed flask is placed in an oven at60° C. over night for the cation exchange. The solution is cooled downto room temperature and three drops of a 0.5 wt. % ethanolicphenolphthalein solution are added as an indicator. The solutionincluding the membrane pieces are titrated with a sodium hydroxidesolution having a concentration of 0.1008 mol/l until the firstincidence of a pink coloration. If the color fades after 30 seconds,additional drops of the sodium hydroxide solution are added until thepink color persists. The IEC is calculated according to the followingequation (V(NaOH) is volume of the NaOH solution and c (NaOH is theconcentration of the NaOH solution):

${I\; E\;{C\left\lbrack {{meq}/g} \right\rbrack}} = \frac{{{c({NaOH})}\left\lbrack {{mol}/l} \right\rbrack} \cdot {{V({NaOH})}\lbrack{ml}\rbrack}}{{m\left( {{dry}\mspace{14mu}{polymer}} \right)}\lbrack g\rbrack}$The titration is repeated 5 times for each polymer analyzed.2. Determination of the Water Uptake

Membrane pieces with a size of about 1 cm² are placed in water at apredetermined temperature and equilibrated for several hours. The wetmembrane pieces are padded dry with a paper wipe and weighed with abalance having an accuracy of ±1 μg. The water uptake is calculatedaccording to the following equation:

${{water}\mspace{14mu}{{uptake}\lbrack\%\rbrack}} = {\frac{{{m\left( {{wet}\mspace{14mu}{polymer}} \right)}\lbrack{mg}\rbrack} - {{m\left( {{dry}\mspace{14mu}{polymer}} \right)}\lbrack{mg}\rbrack}}{{m\left( {{dry}\mspace{14mu}{polymer}} \right)}\lbrack{mg}\rbrack} \cdot 100}$The measurement is conducted with five pieces for each polymer analyzed.3. Measurement of the Specific Conductivity:

The specific conductivity measurements are conducted at differenttemperatures and different relative humidities or in water at differenttemperatures. The analyzed membranes are in the sulfonic acid form. Theimpedance is measured with a 4-probe setup. Specifically, ACmeasurements are carried out at a fixed frequency of 1 kHz with a FlukeRCL meter PM6304. The specific conductivity can be calculated accordingto the following equation

${\sigma\left\lbrack {S/{cm}} \right\rbrack} = {{\frac{1}{Z}\frac{l_{SE}}{w_{M} \cdot t_{M}}} = \frac{200}{{Z\left\lbrack {k\;\Omega} \right\rbrack} \cdot {w_{M}\lbrack{mm}\rbrack} \cdot {t_{M}\left\lbrack {\mu\; m} \right\rbrack}}}$where W_(M) is the width and t_(M) the thickness of the membrane andI_(SE) is the distance between the two sensor electrodes which is fixedat 20 mm for this sample holder. A Teflon cap is placed on top of themembrane by pressing the membrane with a clamp.4. Measurement Conditions

a. In Water

Measurements in water are performed by first equilibrating the membranesample in water to ensure that the sample is at a uniform temperature. Auniform temperature is necessary because clamping of the membraneagainst the electrodes in the sample holder the measurement would beinaccurate if the membrane does not swell homogenously in all directionsat elevated temperatures. The width and thickness is measured after thesample is released from the sample holder. The impedance readings aretaken after the values stabilize without significant change.

b. At Defined Relative Humidities

The relative humidity (“R.H.”) is determined by using saturated saltsolutions. Polymer samples are is placed in a sample holder positionedabove the salt solution. Adjustment of a specific humidity requires theuse of a closed container. The following saturated salt solution areused for producing the R.H. at 80° C. (ASTM, E104-02):

Salt NaCl NaBr MgCl₂ R.H. @ 80° C. 74% 51% 26%

With reference to FIG. 1, a comparison of the specific conductivitiesfor a triblock copolymer with hydrophilic block according to structure 8and hydrophobic block according to structure 17 (Example 1), a triblockcopolymer with hydrophilic block according to structure 9 andhydrophobic block according to structure 17 (Example 2), and amultiblock copolymer with hydrophilic block according to structure 8 andhydrophobic block according to structure 17. FIG. 2 provides plots thatcompare water uptake at room temperature vs. determined IEC of the samepolymers. FIG. 1 shows that triblock copolymers (Example 1) exhibitsimilar proton conductivities as multiblock copolymers at significantlylower IEC. Triblock copolymers with more sulfonic acid groups perrepeating units (Example 2) show these conductivities at even lower IEC.At the same time, the plot in FIG. 2 shows that there is a relationshipbetween water uptake and IEC, which is similar for all polymers shown,although there is some scatter of data. A comparison of the data inFIGS. 1 and 2 leads to the conclusion that triblock copolymers,especially those with an increased number of sulfonic acid groups perrepeating unit, require less water and therefore less swelling toachieve the same conductivity as multiblock copolymers. This is veryimportant for the use of such membranes in fuel cells, since reducedswelling is beneficial for durability, particularly if the fuel cellsare used for automotive applications, where they are exposed to varyinglevels of humidity. Excessive swelling and deswelling of the membrane inpresence of changing levels of water can lead to damage of themembrane-electrode assembly or the gas diffusion layer. Therefore,triblock copolymers such as the ones described in this invention presenta significant improvement.

EXAMPLE 1 Synthesis of Triblock Copolymer Having Formula 24

A) Preparation of Block Having Formula 25

2,2-Bis-(4-hydroxy-phenyl)-propane (46.498 g, 0.2037 mol),1,3-Bis-(4-fluorbenzoyl)benzene (65.648 g, 0.2037 mol), p-cresol (0.5523g, 0.0051 mol, purity: 99.7%), potassium carbonate (62.70 g, 0.4537mol), 360 ml anhydrous N-methyl-pyrrolidone and 75 ml anhydrouscyclohexene are added to a 1000 ml flask equipped with a Dean-Starktrap, a reflux condenser and a nitrogen inlet. The mixture is refluxedat 140° C. for 3 hours under a nitrogen atmosphere. Cyclohexene isremoved and the mixture is heated for another 20 hours at 180° C. Themixture is filtered, diluted with 150 ml NMP and 150 ml tetrahydrofuranand poured into 3 l methanol. The precipitated solid is washed with 1 lmethanol, 1 l hot D. I. water and then with 1 l methanol. Finally, thesolid is dried at 100° C. in vacuum. The yield is 100 g (97%).

B) Preparation of Triblock Copolymer Having Formula 24 (Side and MainChain Sulfonation, Calc. IEC=1.6 meq/g)

Polymer block having formula 25 (30.57 g, ca. 0.0015 mol), thesulfonated THPE side chain monomer having formula 26 (14.821 g, 0.0201mol), 4,4′-Difluoro-3,3′-di(potassium sulfonate)-benzophenone (9.475 g,0.0208 mol) and potassium carbonate (6.34 g, 0.046 mol), 180 mlanhydrous DMSO, 270 ml anhydrous NMP and 80 ml anhydrous benzene areadded to a 1000 ml flask equipped with a Dean-Stark trap, refluxcondenser and a nitrogen inlet.

The mixture is refluxed at 140° C. for 4 hours under nitrogen. Thebenzene is removed and the mixture is heated for further 36 hours at160° C. The mixture is filtered, diluted with DMSO and acidified withconcentrated HCl. The solution is then poured into an excess amount ofmethanol under vigorous stirring. The precipitated solid is washed withmethanol and dried at 100° C. in vacuum. The yield is 47 g (88%).Membranes having a thickness of about 50 μm are cast from a DMSOsolution and dried at 120° C. After removing the membranes from theglass plate, the membranes are annealed at 200° C. under vacuum. An IECof 1.3 meq/g is determined by titration.

Example 2 Synthesis of Triblock Copolymer Having Formula 27 (Four FoldSide Chain Sulfonation, Calculated IEC=1.8 meq/g)

The block polymer having formula 25 (from Example 1A) (4.50 g, ca.0.0002 mol), the fourfold sulfonated THPE side chain monomer havingformula 28 (1.930 g, 0.0020 mol), 4,4′-difluoro-3,3′-di(potassiumsulfonate)-benzophenone (0.946 g, 0.0021 mol), potassium carbonate (0.63g, 0.0046 mol), 10 ml of anhydrous NMP, 50 ml of anhydrous DMSO and 25ml of anhydrous benzene are added to a 100 ml flask, equipped with aDean-Stark trap, a reflux condenser and a nitrogen inlet.

The mixture is refluxed at 140° C. for 3 hours under nitrogen. After thebenzene is removed the mixture is heated for 36 hours at 160° C. Thereaction mixture is filtered, acidified with concentrated HCl and pouredinto 0.6 l methanol under vigorous stirring. The precipitated solid iswashed with methanol and dried at 100° C. in vacuum. The yield is 5.6 g(77%). Membranes having a thickness of about 30 μm are cast from a DMSOsolution and dried at 120° C. After the membranes are removed from theglass plate, the membranes are additionally annealed at 200° C. undervacuum. The IEC of 1.0 meq/g is determined by titration.

Example 3 Synthesis of Triblock Copolymer Having Formula 29

A) Preparation of Block Having Formula 30

4,4′-(hexafluoroisopropylidene)-diphenol (36.962 g, 0.1099 mol),4,4′-difluorobenzophenone (13.987 g, 0.1099 mol), p-cresol (0.2990 g,0.0028 mol, purity: 99.7%), potassium carbonate (34.0 g, 0.246 mol, 130ml anhydrous N-methyl-pyrrolidone (15 wt.-% of reactive solids) and 50ml anhydrous cyclohexene are added to a 500 ml flask equipped with aDean-Stark trap reflux condenser, a reflux condenser and a nitrogeninlet. The mixture is refluxed at 140° C. for 3 hours under nitrogenatmosphere. Cyclohexene is removed, and the mixture is heated forfurther 20 hours at 180° C. The mixture is filtered, diluted with 50 mlNMP and 50 ml tetrahydrofuran and poured into 1.5 l methanol. Theprecipitated solid is washed with 1 l methanol, 1 l D. I. water (70-80°C.), 1 l methanol and dried at 100° C. in vacuum. The yield is 51 g(91%).

B) Preparation of Triblock Copolymer Having Formula 29 (CalculatedIEC=2.3 meq/g)

The polymer block having formula 30 (4.50 g, ca. 0.0002 mol), thetwofold sulfonated THPE side chain monomer having formula 26 (4.175 g,0.0057 mol), 4,4′-Difluoro-3,3′-di(potassium sulfonate)-benzophenone(2.624 g, 0.0058 mol), potassium carbonate (1.75 g, 0.013 mol), 55 mlanhydrous NMP, 35 ml of anhydrous DMSO and 40 ml of anhydrous benzeneare added to a 250 ml flask, equipped with a Dean-Stark trap, a refluxcondenser and a nitrogen inlet. The mixture is refluxed at 140° C. for 3hours under nitrogen. After the benzene is removed the mixture is heatedfor 36 hours at 160° C. The reaction mixture is filtered, acidified withconcentrated HCl and poured into an excessive amount of methanol undervigorous stirring. The precipitated solid is washed with methanol anddried at 100° C. in vacuum. The yield is 8.8 g (80%). Membranes having athickness of about 30 μm thick are cast from a DMSO solution and driedat 120° C. After the membranes are removed from the glass plate, themembranes are additionally annealed at 200° C. under vacuum. The IEC of2.0 meq/g is determined by titration.

Example 4 Synthesis of Triblock Copolymer Having Formula 31

A) Preparation of Polymer Block Having Formula 32

Bis-(4-fluorophenyl)-sulfone (43.2443 g, 0.1701 mol),4,4′-Thiobisbenzenethiol (41.6219 g, 0.1662 mol), p-thiocresol (0.4849g, 0.0039 mol, purity: 99%), potassium carbonate (51.1 g, 0.37 mol), 330ml anhydrous N-methyl-pyrrolidone (15 wt.-% of reactive solids) and 50ml anhydrous cyclohexene are added to a 1000 ml flask equipped with aDean-Stark trap reflux condenser, a reflux condenser and a nitrogeninlet. The mixture is refluxed at 140° C. for 3 hours under nitrogenatmosphere. Cyclohexene is removed, and the mixture is heated forfurther 4 hours at 160° C. The mixture is acidified with concentratedHCl and poured into 3 l methanol. The precipitated solid is washed with1 l methanol, 1 l D. I. water (70-80° C.), 1 l methanol and dried at100° C. in vacuum. The yield is 76 g (96%).

B) Preparation of Triblock Copolymer Having Formula 31 (CalculatedIEC=2.3 meq/g)

The polymer block having formula 32 (2.01 g, ca. 0.0001 mol),Bis-(4-fluoro, 3-(potassium sulfonate)-phenyl)-sulfone (4.127 g, 0.00841mol), 4,4′-Thiobisbenzenethiol (2.119 g, 0.00846 mol), potassiumcarbonate (2.57 g, 0.019 mol), 70 ml of anhydrous NMP and 40 ml ofanhydrous benzene are added to a 250 ml flask, equipped with aDean-Stark trap, a reflux condenser and a nitrogen inlet. The mixture isrefluxed at 140° C. for 3 hours under nitrogen. After the benzene isremoved the mixture is heated for 4 hours at 120° C. The reactionmixture is filtered, acidified with concentrated HCl and poured into anexcessive amount of methanol under vigorous stirring. The precipitatedsolid is washed with methanol and dried at 100° C. in vacuum. The yieldis 4.5 g (56%). Membranes having a thickness of about 60 μm are castfrom a NMP solution and dried at 120° C. The IEC of 1.9 meq/g isdetermined by titration.

While embodiments of the invention have been illustrated and described,it is not intended that these embodiments illustrate and describe allpossible forms of the invention. Rather, the words used in thespecification are words of description rather than limitation, and it isunderstood that various changes may be made without departing from thespirit and scope of the invention.

1. An ion conducting membrane comprising: a block copolymer including apolymer having formula (1):A_(m)-B_(n)-C_(p)  (1) wherein: A is a first polymer segment that isrepeated m times to form first polymer block A_(m) that is eitherhydrophobic or hydrophilic; B is a second polymer segment that isrepeated n times to form second polymer block B_(n) that is eitherhydrophobic or hydrophilic; C is a third polymer segment that isrepeated p times to form third polymer block C_(p) that is eitherhydrophobic or hydrophilic, m, n, and p are each independently aninteger from 1 to 200; with the proviso that when A is hydrophobic, B ishydrophilic and C is hydrophobic; or when A is hydrophilic, B ishydrophobic and C is hydrophilic, wherein when A is hydrophilic, Acomprises a first substituent for proton transfer, when B ishydrophilic, B includes a second substituent for proton transfer, andwhen C is hydrophilic, C includes a third substituent for protontransfer and wherein when A_(m) and C_(p) are both hydrophilic, A and Care each independently described by formula (2) or when B_(n) ishydrophilic, B is described by formula (2):

Y¹ is —O—, —S—, —CO—, —SO₂—, —C(CH₃)₂—, or —C(CF₃)₂—, —PO(T¹)-,—C(CH₃)(T¹)-, —PO(R⁴)—, diphenyl methylene, diphenyl silicon, fluorenyl,an alkylene, a bond directly to the next aromatic ring, or

R¹, R², and R³ are each independently H, C₁₋₁₀ alkyl, C₆₋₁₈ aryl, C₆₋₁₈aralkyl, —SO₃H, —SO₃ ⁻M⁺, —COOH, —COO⁻M⁺, —PO₃H₂, —PO₃H⁻M⁺, —PO₃ ²⁻M₂ ⁺,or —PO₃ ²⁻M²⁺; M is a metal, ammonium or alkylammonium; R⁴ is H, C₁₋₁₀alkyl, C₆₋₁₈ aryl, or C₆₋₁₈ aralkyl; T¹ is given by H or formula (3):

Y² is —O—, —S—, —CO—, —SO₂—, —C(CH₃)₂—, or —C(CF₃)₂—, —PO(R⁴)—, diphenylmethylene, diphenyl silicon, fluorenyl, an alkylene, or a bond directlyto the next aromatic ring; R⁵, R⁶, R⁷, R⁸, R⁹, R¹⁰, R¹¹, R¹², and R¹³are each independently H, C₁₋₁₀ alkyl, C₆₋₁₈ aryl, C₆₋₁₈ aralkyl, SO₃H,—SO₃ ⁻M⁺, —COOH, —COO⁻M⁺, —PO₃H₂, —PO₃H⁻M⁺, —PO₃ ²⁻M₂ ⁺, or —PO₃ ²⁻M²⁺;and j is an integer from 1 to 30, with the proviso that when j>1, the Y²between sequential aromatic rings are the same or different and the R⁵,R⁶, R⁷, R⁸, and R⁹ on sequential aromatic rings are the same ordifferent; wherein at least one of R⁵, R⁶, R⁷, R⁸, R⁹, R¹⁰, R¹¹, R¹²,and R¹³ is —SO₃H, —SO₃ ⁻M⁺, —COOH, —COO⁻M⁺, —PO₃H₂, —PO₃H⁻M⁺, —PO₃ ²⁻M₂⁺, or —PO₃ ²⁻M²⁺; and wherein when A_(m) and C_(p) are both hydrophobic,A and C are each independently described by formula (4) or when B_(n) ishydrophobic, B is described by formula (4):

wherein: Y³ is —O—, —S—, —CO—, —SO₂—, —C(CH₃)₂—, —C(CF₃)₂—, —PO(T¹)-,—C(CH₃)(T¹)-, —PO(R⁴)—, diphenyl methylene, diphenyl silicon, fluorenyl,an alkylene, a bond directly to the next aromatic ring, or

R¹⁴, R¹⁵, R¹⁶, and R¹⁷ are each independently H, C₁₋₁₈ alkyl, C₆₋₁₈aryl, or C₆₋₁₈ aralkyl; k is an integer from 1 to 30; with the provisothat when k>1, the Y³ between sequential aromatic rings are the same ordifferent and the R¹⁴, R¹⁵, R¹⁶, and R¹⁷ on sequential aromatic ringsare the same or different; and i is an integer from 1 to 6; with theproviso that when i>1, the Y¹ between sequential aromatic rings are thesame or different; the T₁ on sequential aromatic rings are the same ordifferent and the R¹, R², and R³ on sequential aromatic rings are thesame or different; wherein for at least one aromatic ring in formula(2), either T¹ is not H or one of R¹, R², or R³ is —SO₃H, —SO₃ ⁻M⁺,—COOH, —COO⁻M⁺, —PO₃H₂, —PO₃H⁻M⁺, —PO₃ ²⁻M₂ ⁺, or —PO₃ ²⁻M²⁺, whereinformula (2) includes a Y¹ selected from the group consisting of—PO(T¹)-, and —C(CH₃)(T¹)- with T¹ given by formula (3).
 2. The ionconducting membrane of claim 1 wherein the first, second, and thirdsubstituents for proton transfer each independently include when presentan acidic substituent or salt thereof.
 3. The ion conducting membrane ofclaim 1 wherein the first, second, and third substituents for protontransfer each independently include when present a component selectedfrom the group consisting of —SO₃H, —SO₃ ⁻M⁺, —COOH, —COO⁻M⁺, —PO₃H₂,—PO₃H⁻M⁺, —PO₃ ²⁻M₂ ⁺, —PO₃ ²⁻M²⁺, and combinations thereof, wherein Mis an alkali or alkaline-earth metal, ammonium, or alkylammonium.
 4. Theion conducting membrane of claim 1 wherein the block copolymer has amicrophase separated morphology.
 5. The ion conducting membrane of claim4 wherein the micro-phase separated morphology comprise spheres,cylinders, lamellae, ordered bi-continuous double diamond structures,disordered bicontinuous morphologies, and combinations thereof.
 6. Theion conducting membrane of claim 1 wherein the first ploymer block has amolecular weight from about 5×10² to about 5×10⁵ (g/mol), the secondpolymer block has a molecular weight from about 5×10² to about 5×10⁵(g/mol), and the third polymer block has a molecular weight from about5×10² to about 5×10⁵ (g/mol).
 7. The ion conducting membrane of claim 1wherein when A_(m) and C_(p) are both hydrophilic, A and C are eachindependently selected from the group consisting of polymer segmentsdescribed by formula (5) and formulae (7) through (12), and saltsthereof; or when B_(n) is hydrophilic, B is selected from the groupconsisting of polymer segments described by formulae (5) and formulae(7) through (12), and salts thereof:


8. The ion conducting membrane of claim 1 wherein when A_(m) and C_(p)are each hydrophobic, A and C are each independently selected from thegroup consisting of polymer segments described by formulae (17) through(20) or when B_(n) is hydrophobic, B is selected from the groupconsisting of polymer segments described by formulae (17) through (20):


9. An ion conducting membrane including a block copolymer having formula(1):A_(m)B_(n)C_(p)1  (1) wherein: A is a first polymer segment that isrepeated m times to form first polymer block A_(m) that is eitherhydrophobic or hydrophilic; B is a second polymer segment that isrepeated n times to form second polymer block B_(n) that is eitherhydrophobic or hydrophilic; C is a third polymer segment that isrepeated p times to form third polymer block C_(p) that is eitherhydrophobic or hydrophilic, m, n, and p are each independently aninteger from 1 to 200; with the proviso that when A is hydrophobic, B ishydrophilic and C is hydrophobic; or when A is hydrophilic, B ishydrophobic and C is hydrophilic, wherein when A is hydrophilic, Acomprises a first substituent for proton transfer, when B ishydrophilic, B includes a second substituent for proton transfer, andwhen C is hydrophilic, C includes a third substituent for protontransfer; and wherein when A_(m) and C_(p) are both hydrophilic, A and Care each independently described by formula (21) and B is a hydrophobicpolymer segment; or when B_(n) is hydrophilic, B is described by formula(21) and A and C are each independently hydrophobic polymer segments:

m, n, and p are each independently an integer from 1 to 200; R¹⁹, R²⁰,R²¹, R²², R²³, R₂₄, R²⁵, R²⁶, R²⁷, R²⁸, R²⁹, R³⁰, R³¹, R³², R³³, and R³⁴are each independently H, —SO₃H, —SO₃ ⁻M⁺, —COOH, —COO⁻M⁺, —PO₃H₂,—PO₃H⁻M⁺, —PO₃ ²⁻M₂ ⁺, or —PO₃ ²⁻M²⁺; and M is a metal, ammonium, oralkylammonium.
 10. The ion conducting membrane of claim 9 wherein whenA_(m) and C_(p) are both hydrophobic, A and C are each independentlydescribed by formula (4) or when B_(n) is hydrophobic, B is described byformula (4):

Y³ is —O—, —S—, —CO—, —SO₂—, —C(CH₃)₂—, or —C(CF₃)₂—, —PO(T¹)-,—C(CH₃)(T¹)-, —PO(R⁴)—, diphenyl methylene, diphenyl silicon, fluorenyl,an alkylene, a bond directly to the next aromatic ring, or

T¹ is H or a moiety having at least one substituent for proton transfer;R⁴ is H, C₁₋₁₀ alkyl, C₆₋₁₈ aryl, or C₆₋₁₈ aralkyl; R¹⁴, R¹⁵, R¹⁶, andR¹⁷ are each independently H, C₁₋₁₈ alkyl, C₆₋₁₈ aryl, or C₆₋₁₈ aralkyl;and k is an integer from about 1 to about 30; with the proviso that whenk>1, the Y³ between sequential aromatic rings are the same or differentand the R¹⁴, R¹⁵, R¹⁶, and R¹⁷ on sequential aromatic rings are the sameor different.